U.S. patent number 10,773,962 [Application Number 16/089,258] was granted by the patent office on 2020-09-15 for preparation method for binder-free, coal-based, briquetted activated carbon.
This patent grant is currently assigned to CHINA ENERGY INVESTMENT CORPORATION LIMITED, SHENHUA XINJIANG ENERGY CO, LTD.. The grantee listed for this patent is CHINA ENERGY INVESTMENT CORPORATION LIMITED, SHENHUA XINJIANG ENERGY CO, LTD.. Invention is credited to Jianqiang Chen, Xiaolin Han, Jianrui Li, Jin Li, Xiaodong Lu, Tao Qi, Cheng Wang, Hongqiang Wang, Liangliang Wu, Xintian Xu, Long Zhao, Wei Zhuang.
United States Patent |
10,773,962 |
Chen , et al. |
September 15, 2020 |
Preparation method for binder-free, coal-based, briquetted
activated carbon
Abstract
Disclosed herein is a method for preparing coal-based,
briquetted activated carbon. The method includes subjecting raw
coal to a briquetting process, pulverizing the briquettes into
particles, and performing carbonization and activation to obtain
activated carbon. The briquetting process includes pulverizing raw
coal to produce a feed, feeding the feed into a feed bin for
degassing, adjusting the temperature and the water content of the
feed in the feed bin, and feeding the feed in the feed bin into a
briquetting apparatus for briquetting to form coal briquettes. The
raw coal briquetting process of the preparation method is suited to
a wide variety of coal, including non-caking coal. The preparation
method yields a coal briquette product with a strength greater than
89% without any binder, which is beneficial to improve the strength
and the like of activated carbon.
Inventors: |
Chen; Jianqiang (Xinjiang,
CN), Xu; Xintian (Xinjiang, CN), Zhao;
Long (Xinjiang, CN), Wang; Hongqiang (Xinjiang,
CN), Han; Xiaolin (Xinjiang, CN), Lu;
Xiaodong (Xinjiang, CN), Qi; Tao (Xinjiang,
CN), Zhuang; Wei (Xinjiang, CN), Li;
Jin (Xinjiang, CN), Wu; Liangliang (Xinjiang,
CN), Li; Jianrui (Xinjiang, CN), Wang;
Cheng (Xinjiang, CN) |
Applicant: |
Name |
City |
State |
Country |
Type |
CHINA ENERGY INVESTMENT CORPORATION LIMITED
SHENHUA XINJIANG ENERGY CO, LTD. |
Beijing
Urumqi, Xinjiang |
N/A
N/A |
CN
CN |
|
|
Assignee: |
CHINA ENERGY INVESTMENT CORPORATION
LIMITED (Beijing, CN)
SHENHUA XINJIANG ENERGY CO, LTD. (Urumqi, Xinjiang,
CN)
|
Family
ID: |
1000005053414 |
Appl.
No.: |
16/089,258 |
Filed: |
January 26, 2017 |
PCT
Filed: |
January 26, 2017 |
PCT No.: |
PCT/CN2017/072715 |
371(c)(1),(2),(4) Date: |
September 27, 2018 |
PCT
Pub. No.: |
WO2017/166920 |
PCT
Pub. Date: |
October 05, 2017 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20190119119 A1 |
Apr 25, 2019 |
|
Foreign Application Priority Data
|
|
|
|
|
Mar 31, 2016 [CN] |
|
|
2016 1 0201435 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C01B
32/336 (20170801); B30B 15/308 (20130101); C01B
32/318 (20170801); C01B 32/384 (20170801); B30B
11/16 (20130101) |
Current International
Class: |
C01B
32/336 (20170101); C01B 32/318 (20170101); C01B
32/384 (20170101); B30B 15/30 (20060101); B30B
11/16 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
1033262 |
|
Jun 1989 |
|
CN |
|
1456644 |
|
Nov 2003 |
|
CN |
|
101168694 |
|
Apr 2008 |
|
CN |
|
101402454 |
|
Apr 2009 |
|
CN |
|
101722669 |
|
Jun 2010 |
|
CN |
|
102126722 |
|
Jul 2011 |
|
CN |
|
102126722 |
|
Jul 2011 |
|
CN |
|
102530938 |
|
Jul 2012 |
|
CN |
|
104276570 |
|
Jan 2015 |
|
CN |
|
105692614 |
|
Jun 2016 |
|
CN |
|
105779059 |
|
Jul 2016 |
|
CN |
|
105800610 |
|
Jul 2016 |
|
CN |
|
105883802 |
|
Aug 2016 |
|
CN |
|
S4953601 |
|
May 1974 |
|
JP |
|
S6311512 |
|
Jan 1988 |
|
JP |
|
H01317113 |
|
Dec 1989 |
|
JP |
|
H0421511 |
|
Jan 1992 |
|
JP |
|
2001170481 |
|
Jun 2001 |
|
JP |
|
2006083052 |
|
Mar 2006 |
|
JP |
|
Other References
Google translation CN102126722; Mar. 16, 2020. cited by examiner
.
Extended European Search Report for EP Application No. 17772951.4,
dated Nov. 5, 2019, 9 pages. cited by applicant .
English translation of Notification of Reasons for Refusal for JP
Application No. 2019502127, dated Oct. 29, 2019, 6 pages. cited by
applicant .
English translation of Notice of Preliminary Rejection for KR
Application No. 10-2018-7030771, dated Mar. 26, 2020, 5 pages.
cited by applicant .
International Search Report issued in PCT/CN2017/072715 dated May
5, 2017. cited by applicant.
|
Primary Examiner: Gregorio; Guinever S
Attorney, Agent or Firm: Armstrong Teasdale LLP
Claims
The invention claimed is:
1. A method for preparing coal-based, briquetted activated carbon,
the method comprising: I. briquetting raw coal to obtain coal
briquettes, wherein briquetting comprises: a. pulverizing the raw
coal to obtain pulverized coal, wherein, the average particle size
of the pulverized coal is at least 20 the content of the pulverized
coal with a particle size of up to 80 .mu.m is at least 90 wt %,
and the content of the pulverized coal with a particle size ranging
between 40 .mu.m-80 .mu.m is at least 10 wt %; b. feeding the
pulverized coal into a feed bin of a briquetting apparatus, and
degassing the pulverized coal in the feed bin; c. adjusting the
temperature of the pulverized coal in the feed bin to 50.degree.
C.-100.degree. C. and the water content to 2 wt %-8 wt %; d.
feeding the pulverized coal in the feed bin into the briquetting
apparatus for briquetting to obtain coal briquettes, and II.
crushing and granulating the coal briquettes obtained in step I,
and carbonizing and activating the crushed and granulated coal
briquettes thereby obtaining activated carbon.
2. The method according to claim 1, wherein briquetting further
comprises: e. crushing a portion of the coal briquettes to coal
particles having particle sizes of up to 3 mm and feeding the coal
particles into the feed bin, wherein the coal particles comprise
from 10 wt % to 40 wt % of the mass of the pulverized coal.
3. The method according to claim 2, wherein the pulverized coal in
the feed bin is fed into the briquetting apparatus through a screw
forced feeder and the briquetting apparatus is a double roller
briquetting apparatus.
4. The method according to claim 2, wherein briquetting further
comprises: blending the raw coal before pulverizing, wherein the
grindability index of the raw coal is at least 55%.
5. The method according to claim 2, wherein briquetting further
comprises: feeding the pulverized coal into a stirring bin for
stirring and pre-degassing before the pulverized coal is fed into
the feed bin, wherein the density of the pulverized coal after
pre-degassing is 0.6 kg/L-0.8 kg/L.
6. The method according to claim 2, wherein in the pulverized coal
the content of the pulverized coal with a particle size of up to 80
.mu.m is at least 95 wt %, and the content of the pulverized coal
with a particle size of up to 40 .mu.m is at least 70 wt %.
7. The method according to claim 1, wherein feeding the pulverized
coal into the feed bin comprises using a screw forced feeder and
the briquetting apparatus is a double roller briquetting
apparatus.
8. The method according to claim 7, wherein briquetting further
comprises: blending the raw coal before pulverizing, wherein the
grindability index of the raw coal is at least 55%.
9. The method according to claim 7, wherein briquetting further
comprises: feeding the pulverized coal into a stirring bin for
stirring and pre-degassing before the pulverized coal is fed into
the feed bin, wherein the density of the pulverized coal after
pre-degassing is 0.6 kg/L-0.8 kg/L.
10. The method according to claim 7, wherein in the pulverized coal
the content of the pulverized coal with a particle size of up to 80
.mu.m is at least 95 wt %, and the content of the pulverized coal
with a particle size of up to 40 .mu.m is at least 70 wt %.
11. The method according to claim 1, wherein briquetting further
comprises: a1. blending the raw coal before pulverizing, wherein
the grindability index of the raw coal is at least 55%.
12. The method according to claim 11, wherein briquetting further
comprises: feeding the pulverized coal into a stirring bin for
stirring and pre-degassing before the pulverized coal is fed into
the feed bin, wherein the density of the pulverized coal after
pre-degassing is 0.6 kg/L-0.8 kg/L.
13. The method according to claim 1, wherein briquetting further
comprises b1. feeding the pulverized coal into a stirring bin for
stirring and pre-degassing before the pulverized coal is fed into
the feed bin, wherein the density of the pulverized coal after
pre-degassing is 0.6 kg/L-0.8 kg/L.
14. The method according to claim 13, wherein the pulverized coal
in the stirring bin is fed into the feed bin by a twin screw feeder
or a star valve.
15. The method according to claim 1, wherein in the pulverized coal
the content of the pulverized coal with a particle size of up to 80
.mu.m is at least 95 wt %, and the content of the pulverized coal
with a particle size of up to 40 .mu.m is at least 70 wt %.
16. The method according to claim 1, wherein the pressure in the
feed bin is a negative pressure, and the negative pressure is 1
kPa-3 kPa.
17. The method according to claim 1, wherein the temperature of the
pulverized coal in the feed bin is 70.degree. C.-85.degree. C. and
the moisture content of the pulverized coal is 2 wt %-6 wt %.
18. The method according to claim 1, wherein the crushed and
granulated coal briquettes are subjected to an oxidation treatment
prior to carbonization, wherein the oxidation treatment comprises:
using a mixture of nitrogen and air as the oxidant which has an
oxygen content of 8 vol %-15 vol % and oxidizing the pulverized
coal at 200.degree. C.-250.degree. C. for 1.5 hours-4 hours.
19. The method according to claim 1, wherein carbonizing comprises:
the temperature is 300.degree. C.-500.degree. C., the oxygen
content of the carbonization atmosphere is up to 5 vol %, and the
carbonization time of 1.5 hours-4 hours.
20. The method according to claim 1 wherein activating comprises:
using water vapour as an activation medium and carrying out the
activation reaction at 850.degree. C.-950.degree. C. for a reaction
time of 3 hours-8 hours.
Description
This application claims priority to International Patent
Application No. PCT/CN2017/072715, filed on Jan. 26, 2017, which
claims priority to CN Patent Application No. 201610201435.1, filed
on Mar. 31, 2016, the disclosures of which are hereby expressly
incorporated by reference in their entireties.
TECHNICAL FIELD
The present invention belongs to the field of preparing coal-based
activated carbon, and particularly relates to a preparation method
for binder-free, coal-based, briquetted activated carbon.
TECHNICAL BACKGROUND
Due to the highly developed pore structure and extremely large
specific surface area of activated carbon, its application
developed from decolorization and deodorization for food and
medicine, gas masks, to large-scale use in solvent refining and
recycling, advanced water treatment, flue gas purification and
blood purification etc. The development has brought new and higher
requirements on the properties such as adsorption and strength of
activated carbon.
In addition, in the production of activated carbon, the method of
preparing coal-based activated carbon using coal as raw material
has been widely used. In order to make the obtained activated
carbon have higher strength when used, usually, it is necessary to
carry out a briquetting treatment before the coal is carbonized and
activated. Therefore, high-strength briquetting of coal is also the
basis for the preparation of high-strength activated carbon.
Although pulverized coal briquetting technologies have been widely
used in the deep processing of raw coal, various binders such as
coal pitch still need to be added in most pulverized coal
briquetting technologies, which not only increases the cost, but
also the prepared coal briquettes need to be air-dried or heated
and roasted, thereby reducing the production efficiency; in
addition, since the commonly used binders such as coal pitch and
coal tar will melt and volatilize after being heated, so that the
strength of the final product is not high, and in the production of
activated carbon, residues such as coal pitch will block the pores
of activated carbon, some residues also contain harmful substances,
which is not conducive to improving the quality of activated
carbon, thus limiting the application of non-caking coal in the
preparation of coal-based activated carbon.
At present, the research on the preparation of binder-free,
coal-based activated carbon has become a hot topic. CN101402454A
discloses a preparation method of formed activated carbon, wherein
pulverized coal is subjected to press forming before being
activated by carbonization, however, in order not to add a binder,
a large amount of weak caking coal and strong caking rich coal have
to be added to the pulverized coal raw material. Due to the
addition of a large amount of caking coal, it is necessary to
slowly increase the temperature during the carbonization process to
prevent the particles from foaming and coking during the
carbonization process, and a long activation time is required to
make the obtained activated carbon have a large enough surface
area.
CN1033262A discloses a method for preparing activated carbon
comprising pulverizing non-caking coal to below 10 .mu.m and then
subjecting the pulverized coal to press forming. It is stated in
this patent application that the smaller the particle size after
pulverization of raw coal, the more advantageous it is to increase
the number of contact points per unit weight between the particles
to increase the adhesion between the sub-particles in the
particles. However, the smaller the particle size after
pulverization of pulverized coal, the greater the possibility of
agglomeration. Considering the requirement of moisture in
subsequent press forming, moisture control is difficult, and
pulverization is also difficult, requirements to equipments are
high and the method is difficult to popularize. At the same time,
studies found that too fine particle size of pulverized coal tends
to cause the internal pores to be too fine after briquetting,
affecting the escape of subsequent carbonized volatiles and the
diffusion of gas used for activation into internal pores when
activated carbon is prepared, and thus affecting the yield and
adsorption of the final product.
Therefore, it is necessary to propose a new preparation method for
binder-free, coal-based, briquetted activated carbon.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a preparation
method for a coal-based, briquetted activated carbon, to solve the
problem of affecting the quality of activated carbon due to the
difficulty of preparing suitable coal briquette during the
preparation of coal-based, briquetted activated carbon when no
binders are used in the prior art.
In order to achieve the above object, the present invention adopts
the following technical solutions:
A preparation method for a coal-based, briquetted activated carbon,
the preparation method comprising:
I. subjecting raw coal to a briquetting process to obtain coal
briquettes through a forming process, the briquetting process
comprises:
a. step of pulverizing the raw coal to obtain pulverized coal,
wherein, the average particle size of the pulverized coal is at
least 20 .mu.m, the content of the pulverized coal with a particle
size of up to 80 .mu.m is at least 90 wt %, and the content of the
pulverized coal with a particle size ranging between 40 .mu.m-80
.mu.m is at least 10 wt %;
b. step of feeding the pulverized coal obtained in step a into the
feed bin of a briquetting apparatus, and degassing the feed in the
feed bin;
c. step of adjusting the temperature of the feed in the feed bin to
50.degree. C.-100.degree. C. and the water content to 2 wt %-8 wt
%;
d. step of feeding the feed in the feed bin into the briquetting
apparatus for briquetting to obtain coal briquettes.
II. The coal briquettes obtained in step I are crushed and
granulated, and then subjected to carbonization and activation to
obtain activated carbon.
In the preparation method of the present invention, a wide range of
raw coals is suitable, which can be one or more of non-caking coal,
weak caking coal, weaker medium caking coal, stronger medium caking
coal and strong caking coal. The non-caking coal, weak caking coal,
weaker medium caking coal, stronger medium caking coal and strong
caking coal are well known in the art, i.e. according to the caking
index G, they are classified into non-caking coal when G is 0-5,
weak caking coal when G is 5-20, weaker medium caking coal when G
is 20-50, stronger medium caking coal when G is 50-65, and strong
caking coal when G is greater than 65.
Those skilled in the art understand that the higher the caking
index of the raw coal, the more favorable it is to form coal
briquettes with higher strength, and the lower the caking index of
the raw coal, the more difficult it is to form coal briquettes with
higher strength. By adjusting various aspects of the raw coal, the
briquetting process of the invention achieves success preparation
of coal briquettes with high strength from the raw coal with higher
caking index or the raw coal with lower caking index, and is
particularly suitable for the briquetting of non-caking coal or the
raw coal mainly composed of non-caking coal, for example, all the
raw coal is non-caking coal, or the content of non-caking coal in
the raw coal is more than 50 wt %, such as 60 wt %, 70 wt %, 80 wt
% or 90 wt %, and the remainder can be weak caking coal or the
like. In the present invention, preferably, the raw coal is
non-caking coal; further preferably, the caking index of the
non-caking coal is =2, such as 0, 1, or 2.
In the preparation method of the present invention, step a is to
pulverize the raw coal to obtain pulverized coal having a specific
particle size distribution. Studies have found that when the
pulverized coal has the above particle size distribution, a
reasonable gradation of pulverized coal with different particle
sizes can be achieved during the briquetting process, which can
improve the strength of briquettes. Preferably, in the pulverized
coal obtained in step a, the content of the pulverized coal with a
particle size of up to 80 .mu.m is at least 95 wt %, the content of
the pulverized coal with particle size of up to 40 .mu.m is at
least 70 wt %; further preferably, the average particle size of the
pulverized coal is 20 .mu.m-40 .mu.m, such as 30 .mu.m; more
preferably, the particle size of the pulverized coal is up to 200
.mu.m, such as up to 150 .mu.m, or up to 100 .mu.m. Those skilled
in the art understand that by selecting a corresponding standard
sieve to sieve the pulverized raw coal, the pulverized coal having
the above particle size distribution can be obtained. Those skilled
in the art certainly understand that the raw coal of the present
invention is preferably subjected to treatment such as removal of
gangue and/or reduction of ash prior to use, for example, to make
ash content no more than 6 wt %, such as 2 wt %-5 wt %, or 3 wt
%.
In the preparation method of the present invention, step b is to
feed the pulverized coal into the feed bin of a briquetting
apparatus, and degassing the feed in the feed bin to reduce the air
adsorbed between pulverized coal particles and on the surface of
pulverized coal particles, which is advantageous to increase the
strength of briquettes. Those skilled in the art understand that
the purpose of degassing can be achieved by pumping gas out of the
feed bin (or vacuuming the feed bin), for example, a filter plate
can be placed on the top and/or the side wall of the feed bin (make
sure that the gas can escape but the pulverized coal cannot), and a
vacuuming device is connected to the back of the filter plate to
discharge the gas adsorbed in the pulverized coal through the
filter plate and the vacuum system. Preferably, in step b, the
pressure in the feed bin is a negative pressure, and the negative
pressure is 0 kPa-3 kPa (as understood by those skilled in the art,
since it is a negative pressure, the endpoint value 0 is not
included), for example, 0.6 kPa, 1 kPa or 2 kPa; further
preferably, the negative pressure of the feed bin is adjusted to
2.5 kPa-3 kPa.
In the preparation method of the present invention, step c is to
adjust the temperature and moisture of the pulverized coal so that
the temperature of the material in the feed bin is 50.degree.
C.-100.degree. C., and the moisture content is 2 wt %-8 wt %.
Preferably, the temperature of the material in the feed bin is
70.degree. C.-85.degree. C. and the moisture content is 2 wt %-6 wt
%, such as 3 wt % or 4 wt %. Reasonable moisture content can play
the role of material binder in the subsequent press briquetting
process, and is advantageous to reduce the amount of gas adsorbed
on the surface of pulverized coal particles. However, too high
moisture will affect the bonding between the pulverized coal
particles, and will make the subsequent treatment by degassing
device difficult. In addition, the above temperature range is
advantageous for the softening of the pulverized coal particles,
and further for the briquetting of the pulverized coal particles,
but if the temperature is too high, it will cause the water in the
pulverized coal to escape. Therefore, the above-mentioned degassing
treatment and the adjustment of temperature and moisture are
closely related, and have an important influence on the briquetting
of the pulverized coal respectively. Extensive studies have found
that when the temperature and moisture content of the material in
the feed bin are kept within the above range, it is advantageous
for the bonding and briquetting of the pulverized coal. Those
skilled in the art understand that the process of adjusting the
temperature and moisture can be carried out in the feed bin, or
during other treatment processes and/or the process of conveying
the pulverized coal, for example, adjusting the water content when
pulverizing the raw coal so that the moisture content of the
material in the feed bin meets the requirement, and heating the
pulverized coal during the process of conveying the pulverized coal
so that the temperature of the material in the feed bin meets the
requirement, which are well known in the art and will not be
described herein.
In the preparation method of the present invention, step d is to
feed the feed in the feed bin into a briquetting apparatus for
briquetting. According to a preferred embodiment of the present
invention, the material in the feed bin is fed into the briquetting
apparatus through a screw forced feeder, so that the volume of the
pulverized coal is reduced due to the pressure of the forced feed
screw when it is fed into the briquetting apparatus, and the
adsorbed gas is extruded, thereby facilitating further degassing.
In the present invention, the material can be briquetted in a
variety of ways, such as extrusion forming, compression forming, or
roll forming. Accordingly, there may be a plurality of briquetting
apparatus, which are well known in the art. Preferably, the
briquetting apparatus is a double roller briquetting apparatus;
further preferably, the line pressure between the rollers is 7
t/cm-15 t/cm, preferably 10 t/cm-15 t/cm when briquetting, to
improve the briquetting effect.
According to the preparation method of the present invention,
preferably, the briquetting process further comprises step e,
crushing a portion of the coal briquettes to coal particles having
particle sizes of up to 3 mm, preferably 0.5 mm-2.5 mm, such as 1
mm or 2 mm, and feeding the coal particles accounting for 10 wt
%-40 wt %, preferably 25 wt %-30 wt % of the mass of the pulverized
coal in the feed bin into the feed bin. Studies accidentally found
that, when the above coal particles are briquetted after being
mixed with the pulverized coal, they can form the core of coal
briquette skeleton during the pressing process, thereby effectively
increasing the strength of the coal briquettes.
According to the preparation method of the present invention,
preferably, the forming process further comprises step a1, blending
coal before pulverizing the raw coal in step a, so that the
grindability index of the raw coal is at least 55%, preferably
60%-80%, such as 65% or 75%. The grindability index reflects the
hardness and brittleness of the raw coal. Studies found that it is
beneficial to further improve the subsequent briquetting effect
when the grindability index of the raw coal is adjusted to the
above range by blending coal.
According to the preparation method of the present invention,
preferably, the briquetting process further comprises step b1,
feeding the pulverized coal into a stirring bin for stirring and
pre-degassing before the pulverized coal enters the feed bin of
step b, so that the density of the pulverized coal after
pre-degassing is 0.6 kg/L-0.8 kg/L. For example, a closed stirring
bin is used to stir the pulverized coal, and gases are pumped out
while stirring to facilitate subsequent press forming. According to
a preferred embodiment of the invention, the pulverized coal in the
stirring bin is fed into the feed bin by a twin screw feeder or a
star valve. The twin screw feeder and the star valve have squeezing
effects on the pulverized coal during the process of conveying the
pulverized coal, which is advantageous to reduce the gas adsorbed
by the pulverized coal or mixed with the pulverized coal during
transportation, achieving a smooth transportation of the pulverized
coal.
In the preparation method of the present invention, in step II, the
coal briquettes obtained in step I are crushed and granulated, and
then subjected to carbonization and activation to obtain activated
carbon. Crushing and granulating coal briquettes and subjecting the
granules obtained by granulation to carbonization and activation
are common processing steps in the preparation of activated carbon,
and are well known to those skilled in the art.
According to the preparation method of the present invention, the
material can be crushed and granulated by means well known to those
skilled in the art, for example, using a crusher to crush and
granulate the coal briquettes. Preferably, the particle size of the
material obtained by granulation is 1 mm-10 mm, preferably 6.7 mm-8
mm.
In the present invention, the conditions of carbonization can be as
follows: the temperature is 300.degree. C.-500.degree. C., the
oxygen content of the carbonized atmosphere is up to 5 vol %, and
the carbonization time is 1.5 hours-4 hours. After carbonization,
the strength of material is improved, and some cracked carbon
structures are formed in hydrocarbons, which have a certain
adsorption capacity and will form more developed microporous
structures during the activation process. The conditions of
activation can be as follows: using water vapour as the activation
medium and carrying out the activation reaction at 850.degree.
C.-950.degree. C. for a reaction time of 3 hours-8 hours.
According to a preferred embodiment of the present invention, in
step II, the granulated material is first subjected to an oxidation
treatment prior to carbonization to perform a partial oxidation
reaction in an oxidant. The oxidation treatment conditions of the
present invention can be as follows: using a mixture of nitrogen
and air as the oxidant which has an oxygen content of 8 vol %-15
vol % and oxidizing the material at 200.degree. C.-250.degree. C.
for 1.5 hours-4 hours to control the oxidation of the material to a
lower extent, which is advantageous for the pre-oxidation of the
high-strength granules of the present invention and can reduce the
degree of graphitization and increase the porosity in the
subsequent carbonization process.
Compared with the prior art, the preparation method of the present
invention has the following advantages:
1. the raw coal briquetting process of the present invention is
suited to a wide variety of coal, even using non-caking coal which
is the most difficult coal to be briquetted as the raw coal, a coal
briquette product with a strength greater than 89% still can be
produced without any binder, which is beneficial to improve the
strength and the like of an activated carbon;
2. no binder is added during the briquetting process, which reduces
the cost, also avoids the subsequent air-drying and stoving
process, and improves the production efficiency;
3. in the present invention, there's no need to pulverize the raw
coal to an excessively small particle size in the raw coal
briquetting process, which is favorable for the formation of
internal pores when preparing activated carbon;
4. the present invention is particularly suitable for preparing
activated carbon using non-caking coal or mixed coal mainly
composed of non-caking coal as the raw coal, as the caking index of
the overall raw coal is low, it is conductive to a further
improvement of the quality of activated carbon.
EMBODIMENTS
The present invention will be described in details below with the
combination of examples, but the invention is not limited
thereto.
In the following examples/comparative examples, the
characterization methods of the relevant parameters are described
as follows:
Average particle size-GB/T 19077.1-2008 particle size analysis
laser diffractometry
Grindability index-GB/T 2565-2014 method for determining the
grindability index of coal (i.e. Had Grove method)
Drum strength-measured according to GB/T7702.3-2008.
The characterization methods of the relevant parameters of
activated carbon are described as follows:
Iodine adsorption value-measured according to GB/T7702.3-2008;
Methylene blue adsorption value-measured according to
GB/T7702.6-2008;
Specific surface area-calculated by the BET method;
Strength-measured according to GB/T7072.3-2008.
The remaining parameters are characterized by national standard or
conventional characterization in the field.
In the following examples/comparative examples, raw coal is
selected from one or more of the following coal types:
Xinjiang Hami coal, from Xinjiang Baoli coal mine, its indicators
are: moisture is 5.17 wt %, air drying based ash is 1.31 wt %, dry
ashless based volatiles is 35.54 wt %, caking index is 2, belongs
to non-caking coal, characteristic of coal cinder is 3,
grindability index is 55%;
Long flame coal of Heishan mining area, from Toksun Heishan coal
mine in Xinjiang, its indicators are: moisture is 3.43 wt %, air
drying based ash is 3.52 wt %, dry ashless based volatiles is 37.16
wt %, caking index is 0, belongs to non-adhesive coal,
characteristic of coal cinder is 3, grindability index is 68%.
In the following examples/comparative examples, the briquetting
apparatus is a double roller briquetting apparatus, manufacturer:
BEPEX; model: MS150.
Example 1
(1) Xinjiang Hami coal was pulverized to pulverized coal having an
average particle size of 29 .mu.m and sieved, wherein the content
of the pulverized coal with a particle size larger than 80 .mu.m
was 2.5 wt %; the content of the pulverized coal with a particle
size larger than 40 .mu.m was 28 wt %;
(2) the pulverized coal obtained in step (1) was fed into the feed
bin of the briquetting apparatus, and the material in the feed bin
was degassed to maintain the negative pressure in the feed bin at
2.5 kPa-3 kPa;
(3) the temperature of the material in the feed bin was maintained
at 50.degree. C.-55.degree. C., and the moisture content of the
material in the feed bin was adjusted to 7 wt %-8 wt %;
(4) the material in the feed bin was fed into the briquetting
apparatus for briquetting, and the line pressure between the
rollers was about 11 t/cm-12 t/cm during briquetting to obtain
briquetted material (coal briquette).
The strength of the coal briquette was tested, and the drum
strength thereof was 89.2%.
Example 2
The difference between example 1 and example 2 lies in that the
mixture of Xinjiang Hami coal and Changyan coal of Heishan mining
area in a mass ratio of 1:1 was used as the raw coal in example
2.
The strength of the coal briquette was tested, and the drum
strength thereof was 91.4%.
Example 3
(1) Xinjiang Hami coal and long flame coal of Heishan mining area
were mixed evenly according to a mass ratio of 1:1, and the mixture
was pulverized to pulverized coal having an average particle size
of 35 .mu.m and sieved, wherein the content of the pulverized coal
with a particle size larger than 80 .mu.m was 8.2 wt %; the content
of the pulverized coal with a particle size larger than 40 .mu.m
was 22 wt %;
(2) the pulverized coal obtained in step (1) was fed into a
stirring bin for stirring and degassing, the top of the stirring
bin was provided with a pipeline for pumping out gas, so that the
density of the pulverized coal after stirring reached 0.60
kg/L-0.65 kg/L, and then the pulverized coal in the stirring bin
was fed into the feed bin of the briquetting apparatus through a
star valve;
(3) the material in the feed bin was degassed to maintain the
negative pressure in the feed bin at 2.5 kPa-3 kPa;
(4) the temperature of the material in the feed bin was maintained
at 80.degree. C.-85.degree. C., and the moisture content of the
material in the feed bin was adjusted to 2 wt %-3 wt %;
(5) the material in the feed bin was fed into the briquetting
apparatus through a screw forced feeder for briquetting, the line
pressure between the rollers was about 11 t/cm-12 t/cm when
briquetting, to obtain briquetted material.
The strength of the coal briquette was tested, and the drum
strength thereof was 91.8%.
Example 4
(1) Xinjiang Hami coal was pulverized to pulverized coal having an
average particle size of 22 .mu.m and sieved, wherein the content
of the pulverized coal with a particle size larger than 80 .mu.m
was 2 wt %; the content of the pulverized coal with a particle size
larger than 40 .mu.m was 15 wt %;
(2) the pulverized coal obtained in step (1) was fed into a feed
bin of the briquetting apparatus, and the coal briquette prepared
in example 1 was crushed to coal particles having a particle size
of 1 mm-3 mm, and the coal particles accounting for 25 wt % of the
mass of the pulverized coal in the feed bin were fed into the feed
bin;
(3) the material in the feed bin was degassed to maintain the
negative pressure in the feed bin at 2 kPa-2.5 kPa;
(4) the temperature of the material in the feed bin was maintained
at 50.degree. C.-55.degree. C., the moisture content of the
material in the feed bin was adjusted to 5 wt %-6 wt %;
(5) the material in the feed bin was fed into the briquetting
apparatus through a screw forced feeder for briquetting, the line
pressure between the rollers was about 11 t/cm-12 t/cm when
briquetting, to obtain briquetted material.
The strength of the coal briquette was tested, and the drum
strength thereof was 92.6%.
Example 5
(1) The pulverized coal obtained in step (1) of example 4 was fed
into a stirring bin for stirring and degassing, the top of the
stirring bin was provided with a pipeline for pumping out gas, so
that the density of the pulverized coal after stirring reached 0.75
kg/L-0.80 kg/L;
(2) the pulverized coal in the stirring bin was fed into the feed
bin of the briquetting apparatus through a twin screw feeder, and
the coal briquettes prepared in example 3 was crushed to coal
particles having a particle size of 1 mm-3 mm, and the coal
particles accounting for 35 wt % of the mass of the pulverized coal
in the feed bin were fed into the feed bin;
(3) the material in the feed bin was degassed to maintain the
negative pressure in the feed bin at 2.5 kPa-3 kPa;
(4) the temperature of the material in the feed bin was maintained
at 70.degree. C.-75.degree. C., and the moisture content of the
material in the feed bin was adjusted to 2 wt %-3 wt %;
(5) the material in the feed bin was fed into the briquetting
apparatus through a screw forced feeder for briquetting, the line
pressure between the rollers was about 11 t/cm-12 t/cm when
briquetting, to obtain briquetted material.
The strength of the coal briquettes was tested, and the drum
strength thereof was 94.3%.
Comparative Example 1
Water was sprayed to Xinjiang Hami coal to adjust its water content
to 12 wt %, and then Xinjiang Hami coal was pulverized to material
having an average particle size of 8.1 .mu.m to obtain pulverized
coal. The obtained pulverized coal was fed into the briquetting
apparatus for briquetting, and the line pressure between the
rollers was about 11 t/cm-12 t/cm when briquetting, to obtain
briquetted material.
The strength of briquetted material was tested, and the drum
strength thereof was 90.4%.
Comparative Example 2
Xinjiang Hami coal was crushed to particles below 10 mm, the coal
pitch accounting for 10 wt % of the particles was added, and the
mixture was pulverized and sieved to prepare pulverized coal having
a particle size of 64 .mu.m-80 .mu.m. The obtained pulverized coal
was fed into the briquetting apparatus for briquetting, and the
line pressure between the rollers was about 11 t/cm-12 t/cm when
briquetting, to obtain briquetted material.
The strength of briquetted material was tested, and the drum
strength thereof was 85%
Comparative Example 3
Xinjiang Hami coal was pulverized and sieved to prepare pulverized
coal having a particle size of 64 .mu.m-80 .mu.m, and the coal tar
accounting for 30 wt % of the pulverized coal was added. After
stirring evenly in a blender, the mixture was fed into a plodder to
prepare coal briquettes with standard size. The coal briquettes was
air-dried at 20.degree. C. for 48 hours and then stoved at
200.degree. C. for 2 hours.
The strength of the coal briquettes was tested, and the drum
strength thereof was 91.8%.
Example 6-10
The coal briquettes prepared in examples 1-5 were subjected to
granulation, oxidation, carbonization and activation respectively,
wherein granules having a particle size of 6.7 mm-8 mm were
obtained by the granulation of the coal briquettes.
The oxidizing conditions of the granules were as follows: a mixed
gas of nitrogen and oxygen was introduced into an external-heating
rotary kiln heated by electric, the oxygen content was controlled
to be about 8 vol %, and the reaction was carried out at
220.degree. C. for 4 hours. The carbonization conditions were as
follows: the granules were calcined in the external-heating rotary
kiln heated by electric with flowing nitrogen at 500.degree. C. for
4 hours to be carbonized. The activation conditions were as
follows: in the presence of an activator, i.e. flowing steam having
a flow rate of 1.5 kg of the steam per kilogram of carbonized
particles per hour, the carbonized particles in the rotary kiln
were activated at 900.degree. C. for 4 hours to obtain activated
carbon products.
The above activated carbon products were characterized separately,
as shown in Table 1.
TABLE-US-00001 TABLE 1 Item Example 6 Example 7 Example 8 Example 9
Example 10 Iodine adsorption value 1090 1069 1100 1063 1093 mg/g
Methylene blue 212 198 219 201 219 adsorption value mg/g Specific
surface area 957 947 998 937 1001 m.sup.2/g Strength % 96.4 96.7
96.2 97.1 95.4 Yield 27 27 25 26 25 wt %
* * * * *